I do not really have a huge problem with considering everything API but would prefer not to. Eg we have a PHP & JS API for notifications so developers do not really need to know the markup for notifications. Not having it API would just leave us more flexibility in changing things in the future as we will want to change things in the future again for sure. Eg maybe we want to use another UI framework (based on AngularJS, eg https://material.angularjs.org/latest/#/demo/material.components.autocomplete only an example) and there notifications etc are made completely different. It's rather a random example though. I'm ok with it as long as we're careful what we put on that page.